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    <script>
        let fn = (a) => {
            console.log(a)
        }

        //简写   若形参只有一个可以不需要括号 若函数体只有一行可以不需要花括号和return
        let fn1 = a => a

        fn(1)
        console.log(fn1(1))
    </script>
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